1. Field of Invention
The invention relates to a printhead for inkjet printers and, in particular, to an inkjet printhead structure that has an internal fast ink supply design.
2. Related Art
The widely accepted inkjet chips are either thermal or piezoelectric. Owing to the competition among similar products, researchers are forced to make further improvement and progress in order to make the latest products satisfy new needs, including the inkjet speed and quality. Such things rely on breakthroughs in the new structure design and the material development.
To increase the inkjet speed, one also has to increase the allowable inkjet frequency. The printing quality depends upon the improvement in the ink density. However, it is found that each time an ink droplet is ejected out of a nozzle, roughly 400 μs is needed for new ink to replenish from the ink channel and for the impact to settle down. This phenomenon in turn affects the inkjet energy controls on the next ejection or nearby nozzle ejections, causing instability in the inkjet quality. Researchers further find that such replenish impact induces cross-talks among nearby nozzles. Making the ink channel long and thin may reduce such cross-talks. For example, the ink channel disclosed in the U.S. Pat. No. 4,882,595 uses exactly this idea to ease the replenish impact within 400 μs.
Although the long and thin ink channel design helps reducing cross-talks among adjacent nozzles, nevertheless, they are not completely avoided. On the other hand, the channel pressure is considerably reduced to slow down the ink supply speed, resulting in worse printing quality and lower inkjet frequency.
To prevent the pressure-lowering problem due to the long and thin ink channel, the U.S. Pat. No. 5,308,442 shortens the ink channel and forms a dipped area between the edge of the main ink supply channel and the ink channel. The border of the dipped area is close to the inlet of the ink channel so that ink can be supplied more quickly.
The invention provides an auxiliary ink supply channel so that more ink can be supplied at a closer distance to the inlet, making the ink supply speed faster.